Changing check box value prevents user change (Word 97 SR-2)

I am having some trouble with a form in Word 97 VBA.

My goal is to have a form with a check box, a text box, and a label. If the user types in a value in the text box, then the check box is set to true. The label's caption would change depending on the value of the text box. In testing this code, I can type in the text box and have the check box change to True.

However, once I do that, I am unable to uncheck the check box with the mouse. I know the value is False because I have code which changes the text box's value and the label's caption. However, the box does not visibly look false, which will definitely confuse users.

So, is there something about check boxes that I need to learn? Obviously, I don't fully understand this feature (indeed, there is a lot of VBA I don't know).

PS, as a bonus problem (which I'm going to tackle next), when I make a change to the text box, the value that comes up is always "1." After that first keypress, any other numbers I type in are fine. I'm sure I'll kick myself when I look at this one.